Production of sulphonation derivatives



Patented Mar. 26,

UNlE D STA S- PATENT OFFICE PaonUc'rroN or smgnomrron EIVATIVE EugeneI). Crittenden, Syracuse, N. 'Y., or to The Solvay Process Company, NewYork, N. Y., a corporation of New York No Drawing. Application September12, 1938,

Serial No. 229,531

' claims. (Cl. 260-400) The present invention relates to a process forthe'production of sulphonation derivatives of satess for the productionof alpha-sulphonic acid derivatives of saturated higher fatty acids fromrelatively inexpensive and readily available raw materials. to provide aprocess for the'production of such sulphonation derivatives ofsaturated. higher fatty acids characterized by a particularly goodcolor. Another object of the invention is to provide a process for theproduction of such derivatives which maybe practiced eiiiciently on acommercial scale.

Other objects of the invention will in part be obvious and will inpartappear hereinafter.

It has been found in accordance with the present'invention thatalpha-sulphonic acid derivatives of saturated higher fatty acids .can beefficiently prepared by sulphonating salts of saturated higher fattyacids (i. e., soaps) with sulphur trioxide in the presence of liquidsulphur dioxide.

The presence of the cation in the molecules of the salts not only doesnot interfere with this essentially acidic reaction but, on thecontrary, has

I been found to involve several advantages. Thus, by sulphonating analkali metal salt of a saturated hlgher'fatty acid containing a certainpercentage of alkali metal salts of unsaturated higher fatty acids withsulphur trioxide in liquid sulphur dioxide, a product of better-color(which is indicative of the purity of the product) can be obtained thanwhen sulphonating in this way a saturated higher fatty acid containingthe same percentage of unsaturated higher fattyacids. This is a distinctadvantage since the amount of hydrogenationrequired of a materialcontaining both saturated and unsaturated bodies to be used in theproduction of sulphonation derivatives of comparable quality, isreduced. For example, satisfactory products can be obtained in the pres-'ent process when using as starting materials alkali metal salts ofsaturated higher fatty acids containing- .from five to ten per cent byweight of alkali metal salts of unsaturated higher fatty cent, orbetter, less than two per cent, by weight of alkali metal "salts ofunsaturated higher fatty acids. It appears probable-that the aboveresult is dueito the-fact thatzunsaturated higher fatty-1 A furtherobject of the invention is the water content of the reaction acids inthe form of alkali metal salts are less susceptible to the charring thatordinarily takes place when unsaturated compounds are reacted withsulphur trioxide in the presence of liquid sulphur dioxide underconditions adapted to introduce sulphonic acid groups into saturatedfatty acid bodies. Thepresent process has the further advantage that itcan be made a part of the usual soap-making process merely by theaddition of I hydrogenation, drying and sulphonation steps.

It has been found to be important to control the water content of thesulphonation reaction mixture. As the amount of water present duringspending decrease in the yields of the desired sulcases it is possibleto secure fair yields of sulphonation derivatives in the presence of arelatively large amount of water by increasing the vigor of thesulphonating conditions, such as the temperature, this is unsatisfactorybecause the products obtainable by such procedure are highly colored.For these reasons, it has been found to be preferable to carry out thesulphonation in a reaction mixture containing not more than three percent of water based on the weight of sulphur trioxide used. In fact, forbest results, the water content of the reaction mixture should bereduced as low as is technically feasible. Because alkali metal soaps,which would be the ordinary starting materials in the present process,are diflicult to prepare free from water, it has been found to beimpractical to reduce the water content of the reaction mixture muchbelow two per cent based on the weight of sulphur trioxide used. Inaccordance with optimum procedure, however, mixture is kept at or belowthisfigure.

the sulphonation is increased, there is a corre That this process isproductive of the results noted is surprising from another aspect. Theusual sulphonating procedures, if applied to the sulphonation .of saltsof saturated higherfatty of alpha-sulphonic acids are not obtained atlow temperatures while athigh temperatures serious carbonization of theorganic material occurs. The results obtained with the .flrst two ofthese sulphonating agents appear to be due to the fact that they containcombined water which is deleterious. In the case of chlorsulphonic acid,by-

drochlqric acid is formedtwhich must be removed.

The alpha-sulphonic acid derivatives of saturated higher fatty acidsprepared by the present process constitute valuable detergent, wetting,and the like agents which are active in hard water and in acid andalkaline solutions. Thus, as compared with ordinary soaps,'they are nothydrolyzed to the free fatty acids in acid solutions. Also, they do nothave the disadvantage of soaps of being precipitated in the-form ofsticky curds from solutions containing calcium or magnesium salts whichhave no detergent value, but which constitute impurities. As comparedwith ordinary sulphonated fatty acids obtained by the sulphonation ofunsaturated and/or hydroxy fatty acids, of which the Turkey red oils areoutstanding examples, the derivatives possess considerably superiorwetting and detergent properties and are more stable against hydrolysis.The properties of the derivatives, as compared with the properties ofordinary sulphonated fatty acids, appear to be due to the facts that thesulphonic acid group in the derivatives is at the end of a long carbonchain, and they contain a sulphonic acid group rather than the moreeasily hydrolyzed sulphuric acid ester group. l

The saturated fatty acid salts used as starting materials in the processare preferably alkali metal salts of the saturated fatty acidsobtainable from' naturally occurring fats and oils, of which tallow,cocoanut oil, babassu oil, palm oil, and fish oils, e. g.,-menhaden fishoil, are examples. When starting with a naturally occurring fat or oil,it is ordinarily advisable at some stage of the process to employhydrogenation, since the fats and oils contain glycerides ofunsaturated, as well as saturated, higher fatty acids.

Tallow, for example, contains glycerides of the saturated fatty acids,stearic acid, palmitic acid, and myristic acid, and the glycerides ofthe unsaturated fatty acids, oleic acid and linoleic acid.

These fats or oils can-be subjected to hydrogenation before or afterconversion to the fatty acid salts by saponification with an appropriatealkaline material. The hydrogenation is preferably carried out bycontacting the material to be treated with hydrogen at an elevatedtemperature and at a superatmospheric pressure in the presence of ahydrogenation catalyst; such as nickel. When the fat or oil is subjectedto this treatment, the resulting product is composed substantiallyentirely of glycerides of saturated fatty acids, the unsaturatedglycerides in the material having been saturated. In proceeding in thisway, the saturated glycerides are then converted to the alkali metalsalts of the saturated fatty acids present therein by saponificationwith an appropriate alkali metal compound; e. g., sodium hydroxide.

In accordance with preferred procedure, however, the saturated fattyacid salts used in the process are prepared by saponification of the fator oil whereby, after removal of glycerine, an ordinary soap is obtainedcomprising a mixture of saturated and unsaturated fatty acid 'aikalimetal salts. This mixture is then subjected to hydrogenation in thepresence of a hydrogena tion catalyst to convert the unsaturated fattyacid salts to the corresponding saturated compounds.

This procedure is of advantage since it has been found that thehydrogenation of a mixture of fatty acid salts proceeds with particularefliciency due to the fact that the mixture is substantially free fromfree fatty acids, which appear to have a deleterious efiect on-thehydrogenation catalyst.

'It will be understood of course that the starting material in theprocess may be a salt or a mixture of salts of saturated higher fattyacids from any source provided that these materials do not containsubstantially more than ten per cent by weight of unsaturated fatty acidbodies. In this connection, the term ,saturat'ed higher fatty acids isused herein to denote saturated fatty acids which contain at least 8carbon atoms and which are free from hydroxyl groups. The preferredstarting materials are those derived from saturated fatty acidscontaining '8 to 24, and especially 14 to 18, carbon atoms. These fattyacids may be any of those present in the above fats or oils afterhydrogenation. Examples of suitable saturated higher fatty acids are thefollowing: myristic acid, palmitic acid, stearic acid, arachidic acid,behenlc acid, and lignoceric acid.

As already stated, it is important to carry out the present process inthe absence of a material amount of water. Salts of saturated higherfatty acids prepared by either of the above described methods ordinarilycontain a proportion of water which should be substantially removedprior to sulphonation if commercially satisfactory products are to beobtained. For this reason the salts of the saturated fatty acids areordinarily subjected to a drying treatment, which may be accomplished inany convenient or satisfactory manner, prior to sulphonation. The driedsalts are then subjected to sulphonation by reacting them with sulphurtrioxide in the presence of liquid sulphur dioxide. This is preferablyac complished by dissolving and/or suspending the salts in liquidsulphur dioxide, and then introducing sulphur trioxide, preferably insolution in liquid sulphur dioxide, into the solution or suspension. Atthe completion of the sulphonation,

the sulphonation derivatives are recovered from the remainder of thereaction mixture as such or in admixture with sulphates. For example,the liquid sulphur dioxide maybe distilled off and condensed for use ina succeeding run of the process.

The sulphonation derivatives prepared in this way arealpha-sulphonic'acid derivatives of the saturated higher fatty acidswhose salts were employed as the starting materials. The sulphonationderivatives appear to be predominantly in the forms of the free acids;i. e., they contain a free sulphonic acid group and a'free carboxylicacid group. When the sulphur dioxide is largely removed by distillation,the mixture remaining also contains a proportion of the sulphate of thecation of the fatty acid salt used as the starting material. Since thesulphonation derivatives are preferably employed in the form of theirpartially or wholly neutralized salts, this mixture is treated so as toneutralize the free fatty acids contained therein. To this end it ispreferably dissolved in a minimum of water, residual sulphur dioxide isromoved as by heating or by passing air or steam through the solution,and the desired neutralizing material is introduced into the solution.In this connection it has been found that relatively little charring orother discoloration occurs in the neutralization reaction andconsequently the wholly neutralized salts may be prepared having goodcolor at this stage of the process; it not being necessary in order toobtain products of especially good color to precipitate the partially,neutralized salts from the solution, as is best procedure when the freefatty acids are sulphonated. At the completion of the neutralization, ifthe partiallyneutralized arcane salts have been prepared, they maybeprecipitated from the solution and recovered by filtration; or if thepartially or wholly neutralized salts have been prepared, the solution(or slurry) may be dried, as by means of a spray or rotary drum drier,to form a dry product containing salts of alpha-sulphonic acidderivatives of saturated higher fatty acids admixed with a proportion ofa sulphate of the neutralizing agent. A solution of this product hasvaluable detergent, wetting, and the like properties. The sulphatepresent appears to improve the valuable properties of the product. Ifdesired, salts (in addition to the sulphateformed in the reaction) suchas, for example, sodium sulphate, ammonium sulphate, monosodiumphosphate, disodium phosphate, sodium tetraborate, sodium silicate, andsodium sesquicarbonate, can be added to the product. Also, in certaincases it may be found of advantage to combine the dry product with otherdetergents and/or wetting agents, such as ordinary soaps and othersulphonated products.

In order that the invention may be more fully understood, referenceshould be had to.the following specific examples in which are disclosedprocesses coming within the scope of the present invention. It will beunderstood that these examples are given for illustrative purposesmerely and are not intended as limitations of the invention. The partsare by weight and the temperatures are in degrees centigrade.

Example 1.3l8 parts of sodium stearate (1 mol) containing less than 10per cent by weight of salts of unsaturated higher fatty acids, and 240parts (3 mols) of sulphur trioxide are added to 7170 parts of liquidsulphur dioxide in a vessel provided with a gas-tight sealing means.After the formation of the mixture, the vessel is sealed and the mixtureis allowed to stand in the vessel which is at room temperature. Afterabout 15 hours, the seal is broken and the sulphur dioxide is removed byevaporation and recovered for use in a succeeding run of the process.The mixture remaining in the vessel is introduced into water, heated toremove residual sulphur dioxide, and is neutralized to a pH of about 7with an aqueous solution of sodium hydroxide. The resulting neutralizedmixture is then evaporated to dryness whereby there is obtained a dryproduct comprising essentially the sodium salt of the alpha-sulphonicacid derivative of stearic acid which product has valuable detergent,wetting, and the like properties.

Example 2.Soap is prepared in the usual manner by saponification ofmutton tallow by treatment with caustic soda. The glycerol is separatedand recovered as a by-product. The soap obtained in this way containsabout 48 per cent by weight of unsaturated fatty acid bodies and is thenhydrogenated at a temperature of 200 and under superatmospheric pressureemploying nickel deposited on calcined magnesite as a catalyst andgaseous hydrogen from a suitable source. The hydrogenation is continueduntil the unsaturated bodies are reduced in amount so as to compriseless than two per cent by weight of the soap. One part of the hydro-.

.liquid sulphur dioxide containing one part of sulphur trioxide isintroduced into the resulting solution or suspension. The vessel issealed and the reaction mixture is maintained at a temperature of about35 for a period of 8 hours or until sulphonation is completed asdetermined by separating a small aliquot portion of the reactionmixture, neutralizing an aqueous solution of this portion with causticsoda, and extracting the unreacted material, if any, with ether. At thecompletion of the sulphonation the vessel is opened and the sulphurdioxide is distilled off and recovered for use in a succeeding run ofthe process. The remaining mixture is then finished as described inExample 1 using as the neutralizing agent sufiicient caustic soda tobring the pH of the solution to 7.

Example 3.-Beef tallow is hydrogenated at an elevated temperature andunder supera'tmospheric pressure using a nickel catalyst and hydrogengas from a convenient source (e. g., from a synthetic ammonia plant) andthe substantially completely saturated glycerides obtained are separatedfrom the catalyst by filtration and treated with caustic alkali to forma soap and liberate glycerine which is recovered. The soap obtained inthis way, which contains less than two per cent of salts of unsaturatedhigher fatty acids, is sulphonated and further treated as described inExample 2. A product is obtained possessing valuable detergent, wetting,and the like properties. 1

When proceeding in accordance Withthe general procedure of the aboveexamples it will be understood that additional salts may be added duringthe neutralization and drying procedures (e. g., up to 20 to 50 per centby weight of the sulphonated compound), or, if desired, an excess ofsulphur trioxide over that required in the sulphonation may be used andneutralized with an alkaline material (e. g., a caustic alkali orammonia) to form in situ an inorganic salt constituting a filler.

It will be understood of course that the starting materials employed inthe examples may be replaced by other salts of saturated higher fattyacids and fats or oils; for example, any of those referred to above, Forexample, in place of the sodium stearate emp oyed in Example 1, theremay be used other alkali metal salts of stearic acid, or instead ofthese salts of stearic acid similar salts of any other saturated higherfatty acid, for example, any of those previously mentioned, may be used.Further, in place of the fats employed in Examples 2 and 3 there may beused an equivalent amount of any other suitable fat or oil; e. g., anyof those mentioned above. In this connection, however, it-shou d benoted that a fat or oil containing hydroxylated fatty acids should notbe employed in the present process since the products resulting from thetreatment of such fatty acids are of considerably less value than thesulphonation derivatives of saturated fatty acids. Furthermore, thetreatment of hydroxylated fatty acid with sulphur trioxide in liquidsulphur dioxide under conditions necessary to replace an alpha-hydrogenatom by a sulphonic acid group produces products containing dark-coloredimpurities which are dimcult, if not impossible, to remove. Aspreviously stated, it is important that the saturated fatty acid saltshould not contain more than ten per cent of unsaturated fatty acids. Ifproducts having particularly good color are desired, a saturated fattyacid salt should be used containing less than five per cent, or better,less than two per cent, of salts of unsaturated higher fatty acids.

In place of the neutralizing agents used in the examples, there may beused any other alkaline material capable of reacting with a sulphonicacid group. Thus, sodium carbonate, potassium carbonate, caustic potash,ammonia, and methyl amine can be used for this purpose.

The amount of sulphur trioxide employed in the process can be variedwithin relatively wide limits, but in order to produce satisfactoryyields of the desired products it should not be reduced below 2.5 molsfor each mol of the saturated fatty. acid salt or salts subjected totreatment. For most cases, it is unnecessary to use more than 4 mols ofthis reagent. For most eflicient operation it is generally preferable toemploy from 3 to 3.5 mols of sulphur trioxide for each mol of thesaturated fatty acid salt. As indicated above, however,'an excess of thesulphur trioxide ordinarily does not have a critical effect on theoperativeness of the process and, in some cases where it is desired toform a sulphate in situ, it is of advantage. With respect to the amountof liquid sulphur dioxide required as the solvent medium it will beunderstood that this amount is dependent in large measure upon thesolubility in this medium of the particular saturated fatty acid salt ormixture of salts used as the starting material in the process. Ascompared with the free saturated fatty acids, for example, these saltshave lesser solubility in liquid sulphur dioxide, and, consequently, arelatively large quantity of this solvent medium is usually required.This does not add materially to the cost of the process because thesulphur dioxide may be eiliciently recovered for reuse in a succeedingrun .of the process by distillation and condensation.

As appears from the examples, the sulphonation reaction can be carriedout at ordinary temperatures, and, because of simplicity of operation,such temperatures are usually employed. If desired, however, a higher orlower temperature can be used; for example, temperatures varying from 20to 50 C. are suitable. The time required for the sulphonation reactionis also a variable factor; being dependent upon the specific saturatedfatty acid salt or salts subjected to treatment, the apparatus employed,the temperature, and other conditions. Under ordinary conditions ofoperation, a reaction period of from 3 to 20 hours is suflicient tocomplete the sulphonation.

In the appended claims where a salt of a saturated higher fatty acid" isreferred to it will be understood that this term is intended to includemixtures of such salts as well as single salts.

Since certain changes may be made in the above process without departingfrom the scope of the invention, the above description should beinterpreted as illustrative and not in a limiting sense.

- I claim:

1. The process for the preparation of alphasulphonic acid derivatives ofsaturated higher fatty acids which comprises sulphonating a salt of asaturated higher fatty acid with sulphur trioxide in the presence ofliquid sulphur dioxide 2. The process for the preparation ofalphasulphonic acid derivatives of saturated higher fatty acids whichcomprises sulphonating a salt of a saturated higher fatty acidcontaining from 8 to 24 carbon atoms and containing not substantiallymore than ten per cent of salts of unsaturated higher fatty acids withsulphur trioxide in a reaction mixture in which liquid sulphur ,dioxideis the solvent medium.

sulphonic acid derivatives of saturated higher fatty acids whichcomprises sulphonating an alkali metal salt of a saturated higher fattyacid with sulphur trioxide in the presence of liquid alkali metal saltsof unsaturated higher fatty acids with sulphur trioxide in a reactionmixture in which liquid sulphur dioxide is the solvent medium, saidreaction mixture being free from more than three per cent of water basedon the weight of sulphur trioxide used.

5. The process for the preparation of alphasulphonic acid derivatives ofsaturated higher fatty acids which comprises sulphonating an alkalimetal salt of a saturated higher fatty acid containing not substantiallymore than five per cent of alkali metal salts of unsaturated higherfatty acids with 2.5 to 4 mols of sulphur trioxide for each mol of saidalkali metal salt of a saturated higher fatty acid in a reaction mixturein which liquid sulphur dioxide is the solvent medium, said reactionmixture being free from more than three per cent of water based on theweight of sulphur trioxide used.

6. The process for the preparation of alphasulphonic acid derivatives ofsaturated higher fatty acids which comprises sulphonating an alkalimetal salt of a saturated higher fatty acid containing from 8 to 24carbon atoms and containing not substantially more than ten per cent ofsalts of unsaturated higher fatty acids with sulphur trioxide in areaction mixture in which liquid sulphur dioxide is the solvent medium,said reaction mixture being free from more than three per cent of waterbased on the weight of sulphur trioxide used, mixing .the resultingsulphonation mass with water to form a mixture comprising thealpha-sulphonic acid derivative of the saturated higher fatty acid andsulphuric acid, and neutralizing said alpha-sulphonic acid derivative.

7. The process forthe preparation of alphasulphonic acid derivatives ofsaturated higher fatty acids which comprises hydrogenating a soapconsisting essentially of alkali metal salts of saturated higher fattyacids and unsaturated higher fatty acids but being substantially freefrom salts of hydroxyl-containing higher fatty acids to produce ahydrogenated soap free from more than five per cent of alkali metalsalts of unsaturated higher fatty acids,,sulphonating said hydrogenatedsoap with sulphur trioxide in the presence of liquid sulphur dioxide,and neutralizing the resulting sulphonation products.

8. The process for the preparation of alphasulphonic acid derivatives ofsaturated, higher fatty acids which comprises hydrogenating a soapconsisting essentially of sodium salts of saturated higher fatty acidsand unsaturated higher fattyacids but being substantially free fromsalts of hydroxyl-co ntaining higher fatty acids'to produce ahydrogenated soap free from more than five per cent of salts ofunsaturated higher fatty acids, sulphonating said hydrogenated soap withsulphur trioxide in a reaction mixture in which liquid sulphur dioxideis the solvent medium, said reaction naixture being free from more thanthree per cent of water based on the weight of sulphur trioxide used, toconvert said hydrogenated soap to alpha-sulphonic acid derivatives ofsaturated higher fatty acids, and converting said alpha-sulphonic acidderivatives to the corresponding sodium salts.

9. The process for the preparation of alphasulphonlc acid derivatives ofstearic acid which comprises sulphonating an alkali metal stearatecontaining not substantially more than five per cent of salts ofunsaturated higher fatty acids with sulphur trioxide in a reactionmixture in which liquid sulphur dioxide is the solvent medium, saidreaction mixture being free from more than three per cent of water basedon the weight of sulphur trioxide used.

10. The process for the preparation of alpha sulphonic acid derivativesoi'saturated higher fatty acids whichcomprises sulphonating the saidsodium salt 01 a saturated higher fatty acid' at a temperature of 20 to50 C. in a reaction mixture in which liquid sulphur dioxide is thesolvent medium, said reaction mixture being free from more than threeper cent of water based on the weight of sulphur trioxide used.

EUGENE D. CRI'I'IENDEN.

